Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

047
FXUS63 KLOT 050744
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
244 AM CDT Tue May 5 2026

.KEY MESSAGES...

- Scattered showers through mid-morning near the I-80 and
  I-88/290 corridors. Showers today into early this evening
  south of I-80, especially well south of I-80.

- Much colder, though only slightly below average temps today
  and Wednesday, followed by a moderating trend closer to
  average toward and over the weekend.

&&

.DISCUSSION...
Issued at 244 AM CDT Tue May 5 2026

Cold front has cleared most of our CWA early this morning,
stretching from NW IN southwest to near STL. Pre-frontal band of
showers and thunderstorms has now pushed well south of the area
with skies clearing out over most of the area. This clearing
will be temporary as an area of over IA likely spreads eastward
into northern IL early this morning. These showers are forming
in a region strengthening 800-600mb frontogenesis within the
entrance region of a 120kt upper level jet streak. These
features are progged to quickly translate east this morning with
a band of showers likely affecting an east-west corridor roughly
near I-80 and I-88/290. These showers will likely quickly shift
east of our CWA by late morning with generally dry conditions
expected north of I-80.

Later this morning as that first northern stream jet streak
zips off to the east, the another jet streak is progged to
develop over the Cornbelt as northern stream trough begins to
phase with the sub-tropical jet. The result will be a blossoming
area of showers and thunderstorms from central Missouri east
into downstate IL. The northern flanks of this precipitation
does look like it will brush by our southern CWA, but quite a
large spread in guidance in how far north this shower activity
gets today. Continued chance pops up to about I-80, but the
better rain chances look to stay closer to the Hwy 24 corridor
and points south. This rain should end tonight with dry
conditions expected until later this week.

Cloud cover should be pretty extensive today into tonight,
especially southern CWA, which should keep temps in the 50s
southern CWA today to perhaps getting close to 60 north.
Overall, it looks like we`ll keep a good deal of cloudiness
around tonight into Wednesday, though there will likely be
breaks in the overcast and some mixed sunshine Wednesday.
Despite a bit more sun on Wednesday, highs should still hold in
the 50s as the heart of this colder air mass settles into the
area.

Opted to hold off on introducing frost into the grids Wednesday
night. GFS and ECMWF soundings both have fairly saturated
conditions between 500-300 mb, suggesting that high cloudiness
could be extensive enough to hinder strong radiational cooling
and frost development. Also, ECMWF and NAM both have the surface
high centered farther south, resulting some light southerly
wind. That slight gradient would likely not be much of a factor
if skies end up clearer, but given the cloud cover and potential
for 5kt or so of wind, the threat of frost over interior
northern IL doesn`t look particularly high. If guidance trends
clearer, then later forecast updates will need to consider frost
Wed night for areas well removed from the urban heat island(s).

A trough is progged to move across the region Friday, but with
the Gulf shut down, this system won`t have much moisture and
subsequent instability to work with. Nevertheless, medium range
guidance does suggest forcing with this wave will be sufficient
for showers Friday. If current model trends continue, then pops
will likely need to be boosted Friday into Friday night.

The next shortwave trough looks to be fast on the heels of
Friday`s with warm air advection in advance of the next wave
looking to provide milder temperatures Saturday. That will be
followed by another chance of showers Sat night with a frontal
passage, followed by a return to cooler temps Sunday into
Monday.

- Izzi

&&

.AVIATION /06Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 104 AM CDT Tue May 5 2026

Key Messages:

- A period of rain showers is expected this morning.

- A lake breeze will likely cause a northeasterly wind shift at
  GYY this afternoon and may cause an easterly wind shift at
  ORD and MDW late this afternoon/early this evening.


A band of post-frontal rain showers is expected to develop/move
into the area late overnight and linger for a bit past sunrise.
VFR conditions are generally favored to prevail during this
rain, but there is about a 30-40% chance that MVFR visibilities
are observed for a brief period of time while the rain band
passes over the Chicago metro terminals. Couldn`t rule out an
additional period of rain later today at GYY, but it still
appears that the broader swath of rain in the region this
afternoon will remain south of the terminals.

A lake breeze is also expected to develop this afternoon and
will likely cause a northeasterly wind shift at GYY at some
point. Uncertainty remains regarding when/whether it will reach
ORD and MDW before washing out this evening as west-northwesterly
winds around 10 kts are expected west of the lake breeze
through much of this afternoon, but if it does end up reaching
ORD and MDW, then an easterly wind shift will occur before light
winds settle into a northerly/north-northwesterly direction a
few hours later.

Ogorek

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

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